In medical imaging, increasingly greater temporal and spatial resolutions are achieved. It is therefore possible in magnetic resonance tomography and computed tomography to record high resolution, spatial three-dimensional images of a moving recording area such as for instance the beating heart of a patient. In order for the technically possible resolution also actually to be achievable, the patient must be positioned accordingly on a patient couch. Furthermore, it is also desirable for as quick and low-radiation a recording as possible to position the patient according to the requirements of a specific protocol or a specific medical question.
The positioning of a patient can be assisted using laser light, whereby a laser projects a line onto the patient couch or the patient. For instance, the companies LAP Laser and Laser Components manufacture appropriate lasers. While the positioning with lasers is largely suited to specifying injection sites for an intervention or tissue to be irradiated during radiation therapy, such a positioning for recording a tomographic image only offers a restricted functionality. Therefore the conventional positioning by means of a laser does not take the orientation and precise support position of the patient into account. Furthermore, a positioning in daily clinical practice is to take place quickly and as accurately and in as non error-prone a fashion as possible.
Furthermore, it may be that the patient was basically positioned correctly, but on account of various restrictions of the imaging device, no recording with the selected protocol and the respective positioning is possible. An example here may be a recording as a “Flash-Spiral” with the computed tomograph Somatom Definition Flash by Siemens, in which the patient couch is advanced so quickly that specific travelling times and directions are required. As a result the available area of the patient couch is restricted for a support of the area of the patient to be recorded.
The position of the patient can be controlled by use of a topogram. A topogram is an overview image for planning a further, higher-quality recording. Such an overview image is generally not resolved in a spatial three-dimensional fashion. The recording of a topogram is also associated with radiation exposure to the patient. Unnecessary and repeated recordings of topograms are therefore to be avoided. The recording of a topogram, which, in computed tomography, is also used to calculate parameters for dose modulation during a further tomographical recording, is therefore to already take place in precisely the positioning of the patient, in which the tomographic recording is to be performed.